Low molecular weight polyethylene polyamines are used in a wide variety of applications such as corrosion inhibitors, fabric softeners, lubricating oil additives, fungicides and many others. Despite the utility of polyethylene polyamines, they are currently obtained only as by-products of ethylenediamine manufactured by the reaction of ethylenedichloride with excess ammonia. Since the polyamines are by-products of ethylenediamine preparation, the supply and quality of available polyethylene polyamines are often variable. Generally, high yields of cyclic polyethylene polyamines, e.g., piperazine, aminoethylpiperazine and the like, are produced although it is the noncyclic polyamines such as diethylenetriamine, triethylenetetramine and higher homologs that are commercially desirable. Moreover, since sodium chloride is co-produced in large quantities, separation of the products from the sodium chloride and the handling and disposal of this corrosive inorganic salt requires special measures.
The prior art discloses various attempts to circumvent these difficulties and to provide controllable efficient routes to polyethylene polyamines:
U.S. Pat. No. 3,714,259 discloses the preparation of linear polyethylene amines by contacting ethanolamine with ethylenediamine compounds in the presence of hydrogen and a hydrogenation catalyst. An example of a hydrogenation catalyst is nickel containing copper and chromium components. Significant amounts of water are included in the feedstock, namely 25-50 wt% based on the combined starting ethylenediamine and monoethanolamine.
U.S. Pat. No. 3,766,184 discloses the reductive amination of monoethanolamine by metallic catalyst of iron and nickel and/or cobalt in the presence of hydrogen.
U.S. Pat. No. 4,036,881 discloses the preparation of polyalkylene polyamines by reacting an alkanolamine with an alkyleneamine compound in the presence of a phosphorus containing substance selected from the group consisting of acidic metal phosphates, phosphoric acid compounds and anhydrides and the phosphate esters.
U.S. Pat. No. 4,044,053 is somewhat similar to the '881 patent except that the alkyleneamine compound is present in an excess amount and a diol is used in place of the alkanolamine.
U.S. Pat. No. 4,314,083 discloses a process for selectively preparing predominantly noncyclic polyalkylene polyamines by reacting an alkanolamine with an alkyleneamine compound in the presence of a salt of a nitrogen or sulfur containing substance or the corresponding acid.
U.S. Pat. No. 4,324,917 discloses ion exchange resins containing phosphonic acid functionality as catalysts for the production of polyethylene polyamines by alkylation of alkyleneamines such as ethylenediamine with alkanolamines such as monoethanolamine.
In addition, U.S. Pat. No. 4,405,784 discloses strontium diorthophosphate as catalyst for acid catalyzed organic condensation reactions, for example the conversion of hydroxyethylpiperazine to triethylenediamine.
Although the prior art does show good selectivities to noncyclic polyamine products, attainment of these selectivies usually requires reaction of a molar deficiency of the alkanolamine with a molar excess of the alkyleneamine. Conversely, if a molar excess of the alkanolamine is reacted with a molar deficiency of the alkyleneamine, selectivities to noncyclic polyamines are low, generally less than 50 wt%.
Therefore, a deficiency of the prior art is the requirement of an excess of alkyleneamine, such as ethylenediamine, to generate predominently noncyclic polyamines. Since higher noncyclic polyamines are formed by successive alkylations of alkyleneamine by the alkanolamine, inclusion of excess alkyleneamine dilutes the reaction, and imposes several disadvantages. For instance, in order to obtain a specified level of polyamine production, the feed and reactor systems must have a greater capacity than if the excess alkyleneamine were not included. Additionally, the system for product separation and purification must be larger to remove and recycle the excess alkylenediamine than if the diluent were not included.
The prior art phosphate catalysts suffered from the deficiency that their solubility in the reaction mixture limits process options, since a soluble catalyst cannot be readily localized in a reaction zone, such as a packed bed reactor, and complicates product isolation and recovery, since the catalyst must be separated from the reaction effluent and recycled to the reaction zone.